Extreme ivory poaching in Mozambique have resulted in the rapid evolution of tusklessness in female African elephants, according to a new study.
Researchers say the country’s devastating civil war that lasted from 1977 to 1992 contributed to the rapid evolution as during the war both sides slaughtered elephants for ivory as a way to finance their war efforts.
In the region that’s now Gorongosa National Park, around 90 percent of the elephants were killed. Half the females that survived were naturally tuskless and so they pass the gene for that trait to their female offspring.
Before the war, nearly one in five females in the region were tuskless. Now, half the female population population in Gorongosa are born without a tusk.
“When we think about natural selection, we think about it happening over hundreds, or thousands, of years,” Samuel Wasser, a conservation biologist at the University of Washington said. “The fact that this dramatic selection for tusklessness happened over 15 years is one of the most astonishing findings.”
There are no tuskless males in the region, which suggest that tusks would likely be an X chromosome–linked dominant, male-lethal trait. That means the mutation would be passed exclusively through female elephants, with just one copy needed to cause tusklessness in females and is lethal to male tuskless elephants resulting in their death in utero. That would explain why two-thirds of tuskless female elephants offspring are also female.
“This is an example of how human activity is changing the evolutionary trajectory of species all across the tree of life,” Shane Campbell-Staton, an evolutionary biologist at Princeton University behind the research, told Business Insider. “Humans are the most influential evolutionary pressure in history besides the five major mass extinction events,” he added.
An elephant’s tusk allows it to strip trees of bark, dig holes and find water.
“The tuskless females ate mostly grass, whereas the tusked animals ate more legumes and tough woody plants,” said Robert Pringle, a co-author of the study and biologist at Princeton University. “These changes will last for at least multiple elephant generations.”